There are various installation modes of a solar cell module on a roof, depending on a shape, an area, a direction of the roof and the like. A variety of combinations may be considered; for example, a first solar cell string configured by directly connecting the a-number of modules on an east side, a second solar cell string configured by directly connecting the b-number of modules on a south side, and a third solar cell string configured by directly connecting the c-number of modules on a west side. An output of each of the solar cell strings differs based on the number of solar cell modules and a direction of the sun. There is known a solar power generation system that, in order to uniform voltages input from the solar cell strings, includes a boosting unit (a DC/DC converter) at an input end of an inverter (for example, see Patent Document 1).